Balance bikes aren't even all that necessary and a lot of them are so poorly made that they aren't doing much of anything. Get a decent real bike of the appropriate size and take the pedals off of it (lower the seat so they can sit while both feet are flat on the ground).
Teach the kids to glide. That's it. Start with gliding a few centimeters and work up to gliding multiple meters/feet. Go at whatever pace is comfortable. It could take months or minutes. You'll know when the time is right to put the pedals back on and raise the seat. At that point, you are 5-10 minutes max from riding a bike like a pro.
For my oldest kid, I paid $50 for a "we will teach your kid to ride in ONE HOUR" class and watched them teach it (my kid took 45 minutes). Since then, I've taught little kids, older kids, adults. This stuff really works. It is seriously hard to believe that the old way of teaching people to ride bikes ever existed.